This is something I've gone around and around on. So far, aside from a few pieces that have been displayed on stands or individual cases, a large hunk of my collection is stored in zipper cases in a closet. Obviously this is less than ideal and I've been looking for a way to display/store a good number of knives.
I've looked at the Gerstner chest set that AG Russell sells, but I don't want everything tucked away in drawers. I've looked at curio cabinets, but I wouldn't be able to fit everying in a single cabinet and I don't have room for more than one.
My current thought is a custom built cabinet - with the bottom 2 1/2 -3ft being lockable drawers, then another 3-3 1/2ft of enclosed glass shelving on top. This would give me storage for my collection on the bottom and a nice display setup that I can rotate knives in and out of.
On another note - I've started becoming a little more cognizent of how my knives are going to be displayed when I order them. One way I think knife makers can add value to their knives is to do some kind of complimentary presentation stands/boxes/etc. A really good example of this are the very cool book vaults that Bruce Bump did for some of his cut-n-shoots. Daniel Winkler did a very cool rustic wood & antler display for a knife tomahawk set I have. Tom Ferry did an excellent buckeye burl & blackwood box for one of the Japanese style folders I got from him recently.
Besides making the knives very easy to display, the displays are also very complimentary to the knives.